Leaf-inhabiting endophytic fungi of European Beech (Fagus sylvatica L.) co-occur in leaf litter but are rare on decaying wood of the same host

Many microfungi are able to live in living plant tissues. In contrast to plant pathogens and parasites the so-called endophytic fungi do not cause obvious disease symptoms in their hosts. Nevertheless, they constitute an ubiquitous active component in direct and multitrophic interactions. The present study was conducted to assess the level of overlap of cultivable microfungi in living and decaying tissues of European Beech (Fagus sylvatica L.) from a forest stand in North-Eastern Germany. The focus lay on the hypothesized fall-spring relationship of leaf-inhabiting forest endophytes, which means that endophytes from autumn leaves persist as saprobes in litter or dead wood, sporulate and re-invade living leaves in spring. Fungal cultures were isolated from living leaves, leaf litter and dead wood still attached to the tree by dilution-to-extinction cultivation in the years 2007-2010. Analyses of species identity, species richness and species composition were based on microscopic identification and of sequencing the fungal DNA 'barcode' ITS (internal transcribed spacer). Species richness of litter-inhabiting microfungi equaled that of wood-inhabiting fungi and exceeded that of leaf endophytes. The most distinctive species assemblage was observed on wood, fungal species composition in living leaves and leaf litter were also significantly different from each other. On the other hand a considerable compositional and phylogenetic overlap between leaf and litter fungi was revealed with phylogenetics, cluster analysis and non-metric multidimensional scaling. The taxa accounting most to the similarity between living and decaying leaves belonged to Capnodiales, Xylariales, Diaporthales and Pleosporales. Finally, data from cultivated leaf-inhabiting beech endophytes were compared with a fungal 454 sequence data set from beech phyllosphere. This analysis allowed the partition of species lists into active fungal endophytes, fungal "epiphytes" and dormant fungal propagules.